Organopolysiloxanes which have been prepared by the condensation and/or equilibration of organosilicon compounds that contain Si-bonded oxygen in the presence of phosphonitrile chlorides have been stabilized against changes in viscosity by treating the organopolysiloxanes containing phosphonitrile chlorides or reaction products thereof which promote the condensation and/or equilibration with basic nitrogen compounds. U.S. Pat. No. 4,203,913 to Burkhardt et al, for example, describes a method for stabilizing organopolysiloxanes prepared in the presence of phosphonitrile chlorides by treating the organopolysiloxanes with ammonia or amine compounds.
When organopolysiloxanes containing phosphorus compounds are treated with tertiary compounds (cf. U.S. Pat. Nos. 3,398,176 and 3,839,388), the resultant organopolysiloxanes have a tendency to become discolored, i.e., they first turn yellow and then brown, when heated to temperatures above 150.degree. C.
Therefore, it is an object of the present invention to stabilize organopolysiloxanes against changes in viscosity. Another object of the present invention is to stabilize organopolysiloxanes against changes in viscosity which have been prepared in the presence of phosphonitrile chlorides. Still another object of the present invention is to provide a method for stabilizing organopolysiloxanes prepared in the presence of phosphonitrile chlorides so that they remain colorless and clear for at least 30 days at temperatures up to 150.degree. C. and remain clear for at least 6 months at room temperature. A further object of the present invention is to provide a method for stabilizing organopolysiloxanes prepared in the presence of phosphonitrile chlorides which are free of an unpleasant odor resulting from the use of an amine to stabilize the organopolysiloxanes.